Tape is a known medium or media for the storage of audio, video, and computer information. The information is typically written to and read from the tape magnetically and/or optically. Such tapes are available spooled on individual reels and in single or dual reel tape cassettes/cartridges. The tape in a single reel tape cartridge must be mechanically threaded through the tape path and spooled onto a take-up reel after insertion into a tape device/drive. The tape path for any type of tape cartridge and tape drive includes a tape head in close proximity to the tape. Tape cartridges include an opening through which a tape head from a tape drive is inserted. The tape head has one or more transducer elements for writing to and/or reading from the tape. The tape is driven past the tape head by a capstan, or by direct drive of the tape reels. In current tape cartridges, the tape on the tape path passes the opening for the tape head one time. In other words, one layer or level of tape is presented at the tape head opening when the tape cartridge is inserted into the tape drive. As used herein, the terms "cassette" and "cartridge", and the terms "device" and "drive" are interchangeable.
Cassettes or cartridges including tape are commonly used to back up computer information from all types of computer systems. This is especially common in work environments where the information may be backed up daily. Home computers also may be equipped with tape drives which use tape cartridges to back up computer information. An additional usage for tape and tape cartridges is for the storage of vast amounts of data. In some instances one or more tape cartridges may be used in a library which includes a tape drive coupled with a picking mechanism and a storage area storing a number of tape cartridges accessible by the picking mechanism. The picking mechanism picks the tape cartridges and inserts them into the tape drives when the information on the drive is needed. The picking mechanism removes the tape cartridges from the tape drives and returns them to the storage area when the information is no longer needed.
Magnetic tape drives typically use a reel-to-reel tape transport design, or "tape path", for controllably advancing the tape past an adjacent tape head. The tape is wound upon 2 reels, one reel at each end. The tape is advanced by rotation of such reels. Tension variation and velocity variation in reel-to-reel tape paths can cause many problems in tape drives and tape cartridges. Variations in tape velocity and tension cause vibration. Tape vibration can be characterized according to the propagation velocity of the vibratory mode, the length and geometry of the vibration transmission path, and the terminating conditions of the vibration transmission path. Such vibration in the tape can disrupt the head-tape interface, and thus effects the overall operation and performance of the drive.
Another problem with tape occurs when the tape quickly moves substantially transverse to the tape winding direction. Such movements may have any number of causes but the most common causes appear to be when a hub moves with respect to the base, when the axis of rotation is not coaxial with the hub, and when stagger lined tape is unwound from a hub. Each of these events accelerates the tape in a direction transverse to its travel. The acceleration typically travels down the length of the tape much like when someone quickly moves a long rope up and down. Tape transports are now being provided with track following heads which move to follow the tracks as the tape passes the head. However, when a hub moves and accelerates the tape, the head typically can not be moved fast enough to accommodate a short quick acceleration.
As previously mentioned, many tape cartridges include an opening for the tape head. In current tape cartridges the tape on the tape path passes the opening one time so that one layer or level of tape is presented to the tape head when it is inserted in the opening of the cartridge and is in a transducing position. There is a constant goal to produce a tape cartridge capable of storing more data in a tape cartridge having the same size. One way of increasing the data capacity of a tape cartridge is to place more tape into a tape cartridge. As a result, tapes continually are made from thinner material so that more feet of tape can be wound onto the hubs in a tape cartridge. Handling thinner and thinner tape or media is one of the major problems faced by designers of tape cartridges and tape drives. Tape tension generally must be reduced when a thinner tape is used to avoid certain problems such as over stressing and other damage. With lower tape tension, the tape flies higher with respect to the head at the head/tape interface. The farther the head is from the media the poorer the transitions on the media are. As a result, higher flying tape results in signals having reduced quality.
If higher tensions are maintained on the thinner tape to keep the flying height of the tape lower thereby maintaining good signal quality, tape creep and telescoping of the tape may occur. Telescoping is a phenomenon that occurs when a tape having one longer edge is wound onto a hub. The longer edge is typically ruffled. When winding such a tape onto a hub the longer edge stays at a longer radius and the shorter edge goes to a shorter radius. The end result is that the tape tends spiral toward one of the edges of the hub while it is being wound. The tendency to telescope can result in deformation of the sidewall of a hub.
In many instances, felt pressure pads are provided near the opening in the tape head to control the pressure between the tape and the tape head. Felt pressure control pads have a number of problems. Among the problems include threading the tape in a cartridge having the felt pressure pads. Another problem is that the felt pressure pads generate debris over their life. Still another problem is that as they wear the pressure may change and they also collect debris. During manufacture, there is also control issues with respect to the size and placement of the felt pressure pads.
What is needed is a tape cartridge that uses low tension to accommodate the use of thinner tape. There is also a need for a tape cartridge that does not require felt pressure pads to maintain an adequate tape pressure at the head/tape interface to keep the flying height of the tape low so that good signal quality is maintained. What is also needed is a tape path which dampens out accelerations of the tape in the vertical direction so that a head which track follows will be better able to follow the tracks on the tape.